The present invention relates to a living tissue stimulation circuit that applies an electrical stimulation to a part of a living tissue.
An electrical stimulation device has been studied which adjusts functions of a living body by embedding a stimulation electrode (hereinafter, referred to as an electrode) in a living body and electrically stimulating a part of the living body. Examples of such an electrical stimulation device include an artificial middle ear delivering the vibration of sound to a patient's auditory ossicle and a heart pacemaker being embedded in a patient's chest to suppress an occurrence of irregular heartbeat by applying an electrical stimulation to a heart. A vision regeneration assisting apparatus has been also known which promotes the regeneration of vision by electrically stimulating cells of the retina with an electrical stimulation pulse signal (charge) output from an electrode (JP2010-187747).
In applying an electrical stimulation to the living tissue through the use of such an electrical stimulation device, it is necessary to inject a predetermined amount of charge into cells from an electrode so as to supply the stimulation necessary for the cells. An electrical stimulation pulse signal corresponding to a feeling of stimulation and being output from the electrode is a bipolar electrical stimulation pulse signal (hereinafter, referred to as a bipolar pulse) having amplitudes in the positive and negative (+ and −) directions. The positive and negative (+ and −) polarities of the bipolar pulse are switched through the use of plural semiconductor switches. By switching the polarity of charge (current), the deflection of charge in an electrically-stimulated site is reduced and thus the charge balance is maintained. The electrical stimulation on the living body is suitably carried out.